A Theoretical Study on the Photochromic Mechanism of 1-Phenyl-3-methyl-4-（6-hydro-4-amino-5-sulfo-2,3-pyrazine）-pyrazole-5-one

The photochromic mechanism of 1-phenyl-3-methyl-4-（6-hydro-4-amino-5-sulfo-2,3- pyrazine）-pyrazole-5-one has been investigated using the density functional theory（DFT）. The solvent effect is simulated using the polarizable continuum model（PCM） of the self-consistent reaction field theory. According to the crystal structure of the title compound, an intramolecular proton transfer mechanism from enol to keto form was proposed to interpret its photochromism. Bader＇s atom-in-molecule（AIM） theory is used to investigate the nature of hydrogen bonds and ring structures. Time-dependent density functional theory（TDDFT） calculation results show that the photochromic process from enol to keto form is reasonable. The conformation and molecular orbital analysis of enol and keto forms explain why only intramolecular proton transfer is possible. The results from analyzing the energy and dipole moments of enol form, transition state and keto form in the gas phase and in different solvents have been used to assess the stability of the title compound.     

Photochromic metal complexes of N-methyl-4,4'-bipyridinium: mechanism and influence of halogen atoms

Photochromism of N-methyl-4,4'-bipyridinium (MQ(+)) salts and their metal complexes has never been reported. A series of MQ(+) coordinated halozinc complexes [(MQ)ZnX(3)] (X = Cl (1), Br (2), I (3)) and [(MQ)ZnCl(1.53)I(1.47)](2)(MQ)ZnCl(1.68)I(1.32) (4), with better physicochemical stability than halide salts of the MQ(+) cation, have been found to exhibit different photochromic behaviors. Compounds 1-3 are isostructural, but only 1 and 2 show photochromism. Introduction of partial Cl atoms to nonphotochromic compound 3 yields compound 4, which also displays photochromism. The photochromic response of 1, 2, and 4 indicates the presence of their long-lived charge separation states, which originate from X → MQ(+) electron transfer according to ESR and XPS measurements. Studies on the influence of different coordinated halogen atoms demonstrate that the Cl atom may be a more suitable electron donor than Br and I atoms to design redox photochromic metal complexes.     

Raman study of a liquid crystalline gel consisting of photochromic 4‐methyl‐N‐(4‐n‐heptyloxysalicylidene)aniline and a gelling agent (R,R′)‐1,2‐bis(dodecanoylamino)cyclohexane

A liquid crystalline physical gel has been prepared from the mixture of a nematic liquid crystal and a low molecular mass gelling agent containing a hydrogen‐bonding moiety. The newly synthesized liquid crystalline compound exhibited photochromism in the crystalline solid phase. Although photochromism was not observed in the nematic gel state of the mixture, the lifetime of photochromism in the solid phase became longer, compared with that of a single liquid crystalline compound. Some Raman bands of the mixture showed a marked change in both intensity and frequency through the phase transitions. These bands have been assigned to the vibrational modes related to the core part of molecule.     

12-钼磷酸-葡聚糖包合物固容体的光致变色

通过DSC曲线,IR光谱,电子光谱和XRD谱分析,发现12-钼磷酸与葡聚糖在水溶液中可形成黄色包合物。以ESR,XPS,IR和电子光谱等手段研究此黄色包合物在紫外光照射下的光致变蓝紫色,是由于其光电子转移反应产物多价态钼(Ⅵ,Ⅴ,Ⅳ)配合物呈蓝紫色,而另一产物带部分羰基葡聚糖为无色所致。由DSC曲线,电子光谱,IR光谱和XRD谱测试结果得知,随着光化反应产物的生成,两者分子间产生包合作用,从而提高光致变色的稳定性。     

Synthesis and spectroscopic study on photochromism of a new thiosemicarbazone compound containing pyrazolone

A new photochromic compound 1,3-diphenyl-4-(4'-fluro)benzal-5-pyrazolone-4-ethyl thiosemicarbazone (DP4FBP-ETSC) was synthesized by direct condensation of 1,3-diphenyl-5-pyrazolone with N4-ethyl thiosemicarbazide. The product was characterized by elemental analysis, IR and 1H NMR spectra. The photochromic properties of the compound were studied using time-dependent fluorescence emission spectra, the UV-vis reflection spectra in the solid state and the UV-vis absorption spectroscopy in liquid. The reaction rate constant of compound was also analyzed. The results show that DP4FBP-ETSC can perform photochromism.     

2-羟基-4-氯-1-苯氧基-9,10-蒽醌的合成及其光致变色性研究

报道了2-羟基-4-氯-1-苯氧基-9,10-蒽醌的合成,并通过元素分析、核磁共振谱、质谱和红外光谱确定了结构.通过紫外-可见光谱探讨了其光致变色性以及取代基对蒽醌类化合物光致变色性的影响.     

(C16H20N2)3PMo12O40/PVA复合薄膜的制备及其光化学和电化学性质

(C16H20N2)3PMo12O40/PVA复合薄膜的制备及其光化学和电化学性质;四甲基联苯胺;钼磷杂多酸;聚乙烯醇;光化学性能;电催化活性     

Crystal structure and photochromism of 1-phenyl-3-methyl-4-benzyl-5-one-pyrazole S-methyl thiosemicarbazone

A new organic photochromic compound containing pyrazolone-ring photochromic functional unit: 1-phenyl-3-methyl-4-benzyl-5-one pyrazole S-methyl thiosemicarbazone (PMBP-smtsc) was synthesized. The photochromic properties and photochemical kinetics of PMBP-smtsc have been studied by UV reflectance spectra under irradiation of 365 nm light. The crystal structure analyses of photocolored product show the photochromism is due to the photoisomerization from enol form to keto form through an intermolecular proton transfer.     

有机铵十聚钨酸盐在溶液中的光致变色性质研究

有机铵十聚钨酸盐具有显著的光致变色性质,电子自旋共振研究表明光致变色是由于光照过程中有五价钨生成,发生了光还原反应。本文研究了二异丙胺和六氢吡啶十钨酸盐(分别简写为DIAW_(10)和PIPDW_(10)在溶液中的光致变色性质,考察了水、乙腈、二甲基甲酰胺(DMF)、二甲基亚砜(DMSO)对光致变色性质的影响,对比研究了四丁基铵盐(NBuW_(10))的情况,还测定了不同光照时间下W(V)浓度,可见吸收光谱和循环伏安,提出了光致变色性质与体系中所含活泼氢的定量关系,初步揭示有机铵十聚钨酸盐光致变色的本质。     

一种新的含吡唑啉酮氨基硫脲化合物的晶体结构及其光致变色性质

A new photochromic organic compound of thiosemicarbazone, 4-（p-bromo-α-methylaminothiocarbonyl hydrazonobenzal）-2,5-dihydro-3-mcthyl-5-oxo-1-phcnyl pyrazolc, was synthesized and characterized by elemental analyses, IR, ^1H NMR spectra, and X-ray single-crystal diffraction analysis. The compound exhibited an interesting photochromism in the solid state when irradiated by ultraviolet light at 365 nm. The photochromic kinetics was studied by the time-dependent powder UV-Vis reflectance spectra. The intcrmolecular and intramolecular hydrogcn-bonding interactions may be responsible for the photochromic phenomenon.     

一种新型的光调控磁分子体系的合成与性能研究

将稳定的四甲基咪唑啉氮氧自由基嫁接到新型的光致变色化合物双(6-甲基-3-乙基-3-羟基-1-氧代-2-亚茚满基) (1)的分子母体中, 成功合成了新型多功能化合物1-((6'-甲基-3,3'-二乙基-3,3'-二羟基-1,1'-二氧代-[2,2']-联亚茚满基)-6-基甲基)-4-(4",4",5",5"-四甲基咪唑啉-2"-基)吡啶溴化物 3"-氧化物 1"-氧基(3). 对化合物3的光致变色性质, ESR波谱以及磁性质进行了研究. 化合物3光照后颜色发生变化, ESR信号表现出久期增宽. 变温磁化率的测试结果显示, 化合物3光照后反铁磁相互作用进一步增强. 研究结果表明化合物3的颜色和磁性的变化均可用光照进行调控.     

Bisthienylethenes Containing a Benzothiadiazole Unit as a Bridge: Photochromic Performance Dependence on Substitution Position

A conveniently synthesized photochromic compound, BTB‐1, containing an unprecedented six‐membered 2,1,3‐benzothiadiazole unit as the center ethene bridge, possesses good photochromic performance, with a high cyclization quantum yield and moderate fatigue resistance in solution or an organogel system. The fluorescence of BTB‐1 can be modulated by solvato‐ and photochromism. However, the analogue BTB‐2, in which the dimethylthiophene substituents are relocated to the 5,6‐positions of benzothiadiazole, does not show any detectable photochromism. To the best of our knowledge, this is the first example of six‐membered bridge bisthienylethenes (BTEs) in which the photochromism can be controlled by the substitution position. The photochromism difference is elucidated by the analysis of resonance structure, the Woodward–Hoffmann rule, and theoretical calculations on the ground‐state potential‐energy surface. In a well‐ordered single‐crystal state, BTB‐1 adopts a relatively rare parallel conformation, and forms an interesting two‐dimensional structure due to the presence of multiple directional intermolecular interactions, including C? H???N and C? H???S hydrogen‐bonding interactions, and π–π stacking interactions. This work contributes to several aspects for developing novel photochromic BTE systems with fluorescence modulation and performances controlled by substitution position in different states (solution, organogel, and single crystal).     

ESIPT-regulated Mechanoresponsive Luminescence Process byIntroducing Intramolecular Hydrogen Bond in NaphthalimideDerivatives#br#

Herein, two compounds, 4-2′-hydroxybenzylidenehydrazinyl-N-butyl-1,8-naphthalimide(BN-1) and 4-benzylidenehydra-zinyl-N-butyl-1,8-naphthalimide(BN-2), were synthesized to explore the hydrogen bonding effect on mechanoresponsive luminescent(MRL). The results showed that compound BN-1 exhibited strong emission in solution and solid-state compared with compound BN-2. After grinding, the emission intensity of compound BN-1 sharply decreased by as much as 15 times with an obvious red-shift from 552 nm to 577 nm. The control compound BN-2, by contrast, did not change so much before and after grinding. Single crystal analysis suggests that BN-1 molecule formed strong intramolecular interaction via ―N=N···H―O hydrogen bond with a distance of 0.2632 nm. An excited-state intramolecular proton transfer(ESIPT) based fluorophore featured this intramolecular hydrogen bond. The intramolecular hydrogen bond as well as other intermolecular interactions can rigidify the molecular conformation of compound BN-1 in solid-state, and thus suppress the nonradiative pathways, resulting in strong emission. These intra- and intermolecular interactions were destroyed by mechanical stimuli, accompanied by molecular conformation change that decreases the luminescence and blocks the ESIPT process. The MRL process was also demonstrated by scanning electron microscopy and powder X-ray diffraction. The molecular stacking mode changed from crystalline to a disordered amorphous state after grinding.     

一类西弗碱基光致异构化分子在不同基底上的表面增强拉曼光谱(英文)

由水杨醛衍生得到的Schiff碱由于其具有起因于受激分子内质子转移的光致 (热致 )变色性质而受到了人们的重视 .本文利用表面增强拉曼光谱研究了该类化合物在金、银基底及银溶胶表面上的拉曼光谱 ,比较了不同基底对吸附分子结构的影响     

RuCl3/PPh3催化顺酐加氢为琥珀酸酐的反应机理研究

利用原位^31P NMR,IR技术跟踪了RuCl3/PPh3催化顺酐加氢过程，并考察了酸碱的添加对反应的影响。根据实验结果，提出了在RuCl3/PPh3催化剂体系作用下，顺酐均相加氢生成琥珀酐的反应历程：RuCl3/PPh3在反应体系中生成活性物种RuHCl(PPh3)，顺酐以C＝C双键与Ru-H活性物种配位生成配合物，此配合物分子内氢转移，形成金属烷基化物，该化合物再与氢进行氧化加成，还原脱出产物琥珀酸酐和Ru-H活性物种，完成整个催化循环。     

含偶氮苯类星型液晶化合物的光致变色

The photochromism of a new star-like liquid crystal that was written by Si(AZO)4 centered by Si and containing four butoxyazobenzene mesogens in its periphery was described. The quantum yield, photoisomerization and photo back-isomerization of Si(AZO)4 in CHCl3 and THF are studied by UV/Vis absorption spectra. The results indicate that the photochromism and photo back-isomerization of Si(AZO)4 in CHCl3 and THF were in accordance with the first order kinetics. The photochromism and photo back-isomerization rate constants are 10-1 s-1, which are 107 times larger than that of side-chain liquid crystalline polymers containing the same azobenzene moieties. These results indicate that the star-like structure does not significantly affect the photoisomerization activity of the azobenzene mesogen in its periphery. The kt/kc of Si(AZO)4 is less than that of azobenzene mesogen which shows that the Si(AZO)4 has better photo-reversibility. So the star-like liquid crystal has potential applications and will become a new type photocontrolable switch and information functional material.     

Synthesis, crystal structure and characterization of photochromic 1,2-bis{2-ethyl-5-[2-(1,3-dioxolane)]-3-thienyl}perfluorocyclopentene

A novel photochromic diarylethene, 1,2-bis{2-ethyl-5-[2-(1,3-dioxolane)]-3-thienyl}perfluorocyclopentene (BEDTP), was synthesized and its structure was determined by single-crystal X-ray diffraction analysis. Its photochromic and fluorescent properties were also investigated. The results showed that this compound exhibited reversible photochromism, changing from colorless to magenta after irradiation with UV light both in solution and in the crystalline phase. In hexane solution, the open-ring isomer of BEDTP exhibited relatively strong fluorescence at 400 nm when excited at 282 nm. The fluorescence intensity decreased along with the photochromism upon irradiation with 254 nm light and its closed-ring isomer showed almost no fluorescence.     

Theoretical study on molecular structures, intramolecular proton transfer reaction, and solvent effects of 1-phenyl-3-methyl-4-(6-hydro-4-amino-5-sulfo-2,3-pyrazine)-pyrazole-5-one

The molecular structures and intramolecular proton transfer reaction of 1-phenyl-3-methyl-4-(6-hydro-4-amino-5-sulfo-2,3-pyrazine)-pyrazole-5-one have been investigated with both ab initio method and the density functional theory. The solvent effects are simulated using the self-consistent reaction field (SCRF) method within the framework of the polarizable continuum model (PCM). The results show that the computed geometrical parameters at the B3LYP levels are in better agreement with experimental values than those at the RHF levels, and the choice of functional in DFT plays an important role in describing the title compound. It is found that strong hydrogen bonds (O–H···N and O···H–N) exist in the title compound, and in the proton transfer process, the O–H bond is broken while the N–H bond is formed. In addition, the order of stability of the isomers remains the same in different solvents, while the barrier height of the proton transfer reaction and dipole moments for the title compound grow with the increase of the solvent polarity. Eventually, the NBO analysis shows that the strength of the hydrogen bond reduces with the increase of the solvent polarity.     

Synthesis, crystal structure and optoelectronic properties of a new unsymmetrical photochromic diarylethene

A new unsymmetrical photochromic diarylethene, 1-(2-methyl-5-phenyl-3-thienyl)-2-[2-methyl-5-(3-trifluoromethylphenyl)-3-thienyl]perfluorocyclopentene (1a), was synthesized and its structure was determined by single-crystal X-ray diffraction analysis. Its optical and electrochemical properties, including photochromic reactivity both in solution and in the solid state (PMMA film and the single-crystalline phase), fluorescence and electrochemical properties were investigated in detail. The compound showed excellent photochromism even in the single-crystalline phase by photo-irradiation. In acetonitrile, the open-ring isomer of diarylethene 1 exhibited relatively strong fluorescence at 470nm when excited at 300nm, and its emission intensity decreased along with the photochromism upon irradiation with 313nm light. Its closed-ring isomer showed almost no fluorescence. The electrochemical properties of diarylethene were investigated by performing cyclic voltammetry experiment and its HOMO and LUMO energy level were calculated.     

Metal-Organic Frameworks with Novel Catenane-like Interlocking: Metal-Determined Photoresponse and Uranyl Sensing

The assembly of two tripyridinium-tricarboxylate ligands and different metal ions leads to seven isostructural MOFs, which show novel 2D→2D supramolecular entanglement featuring catenane-like interlocking of tricyclic cages. The MOFs show tripyridinium-afforded and metal-modulated photoresponsive properties. The MOFs with d¹⁰ metal centers ( 1-Cd , 1-Zn , 2-Cd , 2-Zn ) show fast and reversible photochromism and concomitant fluorescence quenching, 1-Ni displays slower photochromism but does not fluoresce, and 1-Co and 2-Co are neither photochromic nor fluorescent. It is shown here that the network entanglement dictates donor-acceptor close contacts, which enable fluorescence originated from interligand charge transfer. The contacts also allow photoinduced electron transfer, which underlies photochromism and concomitant fluorescence response. The metal dependence in fluorescence and photochromism can be related to energy transfer through metal-centered d-d transitions. In addition, 1-Cd is demonstrated to be a potential fluorescence sensor for sensitive and selective detection of UO₂²⁺ in water.